The invention in general relates to scan conversion apparatus, and more particularly, to a display system for sidelooking sonar apparatus. 2. Description of the Prior Art
In sidelooking sonar systems the apparatus traveling over a target area repetitivly transmits acoustic pulses to sonify the target area, and energy reflected from narrow adjacent strips on the target area is protrayed as a line-by-line picture that is a pattern of highlights and shadows analogous to an optically viewed panorama illuminated by side lighting, with objects outlined in such a way as to permit their identification. By increasing the area detected and portrayed for each transmitted pulse, the carrier speed and therefore the search or mapping rate, is significantly increased. This is accomplished by the use of multiple receiver beams.
With such multibeam sidelooking sonar systems, it is desirable to view the target area in real time, such as on a conventional TV monitor. This is accomplished by portraying the sidelooking sonar information as a moving window display on the monitor. One such example of a moving window display is described in U.S. Pat. No. 3,792,194, which illustrates, by way of example, a single beam system wherein the beam is rapidly sampled, stored in a shift register and read out therefrom for placement onto a rotating video disc at a rate compatible with the line rate of the TV monitor.
For use with a multibeam system, the necessary high speed logic required for processing the plurality of the beams would significantly add to the cost of the overall system.
A moving window sonar display is also described in U.S. Pat. No. 3,914,730 in conjunction with multiple receive beams; however, such system provides a plurality of channels, one for each beam, and the channels are rapidly scanned so that no intermediate high speed shift register storage is provided.